Selling an android phone => Need help ... Did a factory reset- not secure enough?

[Varsonic]

Hi,

I'm about to sell my device online and I have a few questions in concerning to security and encryption.

I did a factory reset on the phone, erasing all data and before I created my ad to sell my cell-phone online I did a little research to make sure their is no way for this data to be recovered.
I ended up learning that you are suppose to encrypt the device and then do a factory reset to ensure your data will not be recoverable.

I've already done a factory reset , I'm wondering what happens if i were to encrpyt the device now that it has empty files and just a factory-reset phone and re-did another factory reset?

Basically,

(HTC M8 )Android Phone
=> Lots of personal files

=> Did a factory reset

=> Googled to make sure theirs no way for someone to recover my data
=> Learn about encrypting a phone before doing a factory reset
=> I've already done the factory reset and I have yet to encrypt the phone.
I'm wondering what are the steps to ensure that my previous factory reset data is not recoverable?

What are the steps I have to take to just make sure no one can recover my data =>
E.G my saved passwords, banking information that had gotten "wiped" from my factory reset from the settings.

Thanks,

 

[bruce73]

What I have done is to do a factory reset then format internal storage via recovery or Settings/Storage. I've never encrypted anything.

 

[Mooncatt]

As I'm guessing you found out when searching, the reason you encrypt is because it's like putting a lock on the now jumbled data and the reset throws away the key. If you think about it, if you've ever deleted anything on your phone, there's a chance it could be recovered. My guess is the encryption process covers that data too because the encrypt > reset process seems to be the official line from Google and I've never seen this question brought up before.

If that's the case, it would stand to reason that encrypting a phone that's already been reset should still cover up the extra erroneous data. Doing another reset afterwards would then get your phone effectively wiped.

Just keep in mind that there's no 100% way to prevent recovering data off a device other than physically destroying it. Encrypting and the resetting it is about as safe as you could make it, though, and still be usable.